Bad maths adds up to nuclear scare

About 200 kilograms of plutonium produced by a Japanese nuclear facility - enough to make about 25 nuclear bombs - is "missing", authorities in Tokyo have admitted.

But Japan and the United Nations nuclear watchdog, the International Atomic Energy Agency (IAEA), maintain that the shortfall is the result of miscalculation and measuring errors, rather than the plutonium being diverted for weapons production.

The Japanese Government told the IAEA that since 1977, the Tokai nuclear reprocessing plant had extracted 6890kilograms from spent nuclear fuel - 206kilograms less than initial projects.

Japanese officials say the shortfall is the result of problems in computation of the amount of plutonium, and the dilution of plutonium into waste water. The ministry in charge of the facility denied that any plutonium had been diverted for weapons, but acknowledged the need for better measuring systems.

After hearing from Japan, the IAEA said it accepted the explanations for the shortfall. ");document.write("

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A statement from the agency said that Japan was correcting the amount of plutonium it had declared in past reports.

"The IAEA has recognised for some time that the amount of nuclear material transferred to waste storage has not been adequately measured in the past and has worked with the [Tokai] facility operators and state authorities to introduce improved measurement techniques," the statement said.

The director-general of the agency, Mohamed ElBaradei, said the agency is confident that "no nuclear material has been diverted from the facility".

Japan - which was the target of the world's only nuclear attacks - has a strict policy of no nuclear weapons, although there has been a growing debate with the emerging threat of a nuclear-armed North Korea.

The plutonium controversy is another embarrassment for Japan's nuclear industry, which last year faced a scandal over falsified safety reports.

That came on top of an already poor safety record. The Tokai reprocessing plant is part of a nuclear complex that was the site of a nuclear accident in 1999, which killed two workers and forced hundreds of thousands of people to be evacuated.